Our research investigates lexical representations in long-term memory and the processes that both encode and retrieve those representations in speech perception, production and memory. Most theories assume that speech waveforms are converted to phoneme strings, which are then compared to the mental lexicon. This view emphasizes the abstract properties of words: Speech signals containing idiosyncratic information (e.g., speaker's voice) are normalized into canonical forms, then matched to abstract lexical entries. However, episodic memory theories posit that details of perceptual experiences are not forgotten. Instead, they stored, and they support later perception. The proposed research consists of five specific aims. First, we will prepare a collection of computational models, ranging from strongly episodic to hybrid abstract-episodic models. The remaining four aims correspond to four empirical projects. These experiments test the episodic view using speech perception, production, and memory measures. In Project 1, perception and memory experiments will test factors that affect episodic content, examining roles of selective attention and working memory. The experiments will assess the nature and extent of perceptual-conceptual tradeoffs in memory trace formation. In Project 2, multidimensional scaling experiments are coupled with memory tests, aiming to discover the similarity-distance function in episodic word priming. Project 3 provides critical tests of the episodic view, using eye-tracking procedures to assess the timecourse of episodic effects in perception. Project 4 will examine memory for larger episodic units, using full sentences as stimuli. In addition to standard tests, sentence memory will be assessed using a novel speech-production method, examining the acoustic-phonetic content of spoken responses. Following our previous research, we expect people to spontaneously imitate acoustic patterns of the stimulus sentences. The episodic theory predicts that degrees of imitation will be affected by """"""""abstract"""""""" characteristics of the sentences, such as semantic complexity, suggesting that speech acoustics reflect a complex interplay of linguistic stimuli and their episodic representations. ? ? ?
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